@Danp Good catch, can't believe I missed that.

Unfortunately, that produced a new error;

Error code: SR_BACKEND_FAILURE_77 Error parameters: , Logical Volume group creation failed,

From some googling around it appears the issue is that the disks still have a zfs_member tag on them. lsblk -f produces this:

NAME FSTYPE LABEL UUID MOUNTPOINT sdd zfs_memb ├─sdd2 zfs_memb data 305869021769108511 └─sdd1 zfs_memb sdb linux_ra localhost:127 1d7d1927-dfdb-c8a8-4af1-b25c2b355a7a └─md127 zfs_memb boot-pool 17799519329276801846 ├─md127p5 ext3 logs-efkbam 0deeb614-6788-45f9-92b7-0f6acc05da6d /var/log ├─md127p3 zfs_memb boot-pool 17799519329276801846 ├─md127p1 ext3 root-efkbam 62e0f462-29f8-4c2a-8df7-bed45c144a4a / ├─md127p6 swap swap-efkbam 26a6ce99-d4fd-43d1-8a27-79bddafb8707 [SWAP] ├─md127p4 vfat BOOT-EFKBAM 0B9B-C4C7 /boot/efi └─md127p2 sde zfs_memb ├─sde2 zfs_memb data 305869021769108511 └─sde1 zfs_memb sdc linux_ra localhost:127 1d7d1927-dfdb-c8a8-4af1-b25c2b355a7a └─md127 zfs_memb boot-pool 17799519329276801846 ├─md127p5 ext3 logs-efkbam 0deeb614-6788-45f9-92b7-0f6acc05da6d /var/log ├─md127p3 zfs_memb boot-pool 17799519329276801846 ├─md127p1 ext3 root-efkbam 62e0f462-29f8-4c2a-8df7-bed45c144a4a / ├─md127p6 swap swap-efkbam 26a6ce99-d4fd-43d1-8a27-79bddafb8707 [SWAP] ├─md127p4 vfat BOOT-EFKBAM 0B9B-C4C7 /boot/efi └─md127p2 sda └─sda1

So it appears my next step is sorting that out. Unfortunately the only way of clearing these tags that I've found so far seems to be wiping the drives completely and starting over? If so that's going to suck as I don't have physical access to the machine right now.

If anyone has any suggestions for removing errant zfs_member tags (this machine previously hosted a TrueNAS install) without wiping the whole damn machine, I'd be eager to hear them. If not it'll have to wait until I'm back in the office I guess.

Thank you again @Danp for your help.